Electrostatic recording materials

ABSTRACT

In an electrostatic recording material comprising an electroconductive base sheet having a dielectric layer on which a negatively charged electrostatic image of electrical signal is to be formed, an improvement which is characterized in that said dielectric layer contains at least one of guanidine compounds selected from the group consisting of guanidine, guanidine derivatives and salts thereof in a proportion of 0.05 to 20 weight percent.

United States Patent Tanimoto et al.

ELECTROSTATIC RECORDING MATERIALS Inventors: Tadashi Tanimoto, Amagasaki;

Kazuo Shibata, Nishinomiya, both of Japan Assignee: Kanzaki Paper Manufacturing Company, Ltd., Tokyo, Japan Filed: Mar. 19, 1974 Appl. No.: 452,642

Foreign Application Priority Data Mar. 20, 1973 Japan 48-32025 US. Cl. 427/411; 428/537; 162/138, 252/500 Int. Cl. B32B 9/04; B32B 21/04 Field of Search 117/201; 162/138, 96/1.5 R, 252/500; 428/411, 537; 260/564 References Cited UNITED STATES PATENTS 6/1972 Contois 96/l.5 C

Primary ExaminerMichael F. Esposito Attorney, Agent, or Firm-Armstrong, Nikaido & Wegner [57] ABSTRACT In an electrostatic recording material comprising an electroconductive base sheet having a dielectric layer on which a negatively charged electrostatic image of electrical signal isto be formed, an improvement which is characterized in that said dielectric layer con- .tains at least one of guanidine compounds selected I from the group consisting of guanidine, guanidine derivatives and salts thereof in a proportion of 0. 05 to 20 weight percent.

10 Claims, No Drawings ELECTROSTATIC RECORDING MATERIALS This invention relates to an improvement of electrostatic recording materials, more particularly to improved electrostatic recording materials on which negatively charged electrostatic images corresponding to electrical signals are to be formed.

The electrostatic recording system has recently been widely applied to a facsimile or a computer input-output system or the like as a system suitable for high speed recording in a high speed telecommunication system, a high speed graphic reproduction system, etc. The electrostatic recording material as a recording medium basically comprises a dielectric layer, which serves as an electric-charge-retentive layer, and an electroconductive base sheet which supports the dielectric layer. Electrostatic images of electrical signals formed on the electric-charge-retentive layer are made visible with a developer comprising a toner and a carrier which has a polarity opposite to the polarity of the electrostatic image charge, and fixed as permanent visible images by further treatment.

With the recording system described above, the electrostatic image of electrical signal is formed usually with negative charges and the image is then made visible with a positively charged developer, since if the electrostatic image is to be formed with positive charges, there arise a difficulty to produce negatively charged developer and a need to use a much higher threshold voltage than in the former case, rendering the recording device expensive.

However in the presence of forming a negatively charged electrostatic image on the known electrostatic recording material and developing the image with a positively charged developer, the friction between the surface of electrostatic recording material and the recording stylus, paper feeding roller and developer tends to generate negative static triboelectricity also in the background area. During the developing step, therefore, the positively charged developer is deposited not only on the electrostatic image area but also on the background area having negative triboelectrical charges, with the resulting drawback of giving a high background density.

A main object of this invention is to provide an electrostatic recording material which permits reproduction of clear and 'sharp images with a very low background density.

Other objects and advantages of this invention will be apparent from the following description.

In an electrostatic recording material comprising an electroconductive base sheet having a dielectric layer on which a negatively charged electrostatic image of electrical signal is to be formed, the improvement of the present invention is characterized in that said dielectric layer contains 0.05 to weight percent of at least one of guanidine compounds, said guanidine compound including guanidine, various guanidine derivatives and salts thereof.

Our researches have revealed the novel fact that guanidine, guanidine derivatives or salts thereof, when incorporated in the dielectric layer of electrostatic recording material, do not impair the dielectric characteristics of the dielectric layer itself, consequently permitting the formation of negatively charged electrostatic images without any adverse effect, and are capable of effectively preventing generation of objectionable negative triboelectricity which would otherwise take place in the dielectric layer during the steps of forming the electrostatic images and developing the images obtained. In fact, according to this invention, electrostatic images can be formed in accurately corresponding relation to the electrical signal input, whereas the background area has neutral polarity or is charged to positive polarity opposite to that of the charged image area all the time. Accordingly, when applied to the electrostatic recording material, the positively charged developer is deposited not on the background area but only onthe image area to give clear and sharp visible images with a low background density. Such outstanding effect is achieved only by the use of the guanidine compounds. In contrast, our experiments conducted using various known antistatic agents in place of the guanidine derivatives have shown that they deteriorated the dielectric characteristics of the dielectric layer, making it difficult to obtain electrostatic images accurately corresponding to the electrical signal input. A

The guanidine compounds to be used in this invention include guanidine, various guanidine deriatives and salts thereof. The guanidine and its derivatives are those represented by the following formula:

wherein each of R R R3, R and R is a hydrogen atom, aliphatic hydrocarbon group, alkoxyl group having 1 to 18 carbon atoms, acyl group having 1 to 18 carbon atoms, phenyl group, amino group, guanyl group, nitro group, nitroso group, cyano group or -R' S0 R being a phenyl or alkyl group.

In the above formula (l) the aliphatic hydrocarbon group represented by each of R to R includes an alkyl group having 1 to 18 carbon atoms, preferably 1 to 6 carbon atoms, an alkenyl group having 3 to 12 carbon atoms, preferably 3 to 7 carbon atoms, and an alicyclic group having 4 to 6 carbon atoms, preferably 6 carbon atoms. Preferable carbon atoms of alkoxyl group and acyl group represented by each of R to R are in the range of l to 12. The aliphatic hydrocarbon group, alkoxy group, acyl group, amino group and guanyl group represented by each of R to R may contain a substituent such as a hydroxyl group, alkoxyl group, amino group, phenyl group, carboxyl group, cyano group, nitro group, nitroso group or halogen atom. The phenyl group represented by each of R to R may also contain a substituent such as an alkyl group, halogen atom, nitro group, hydroxyl group, alkoxyl group, amino group, carboxyl group, cyano group or nitroso group. Preferable substituents for the aliphatic hydrocarbon group represented by each of R to R is a hydroxyl group, lower alkoxyl group, amino group or phenyl group. Preferable substituents for the alkoxyl group represented by each of R, to R in a carboxyl group. Preferable substituents for the acyl group represented by each of R to R is a carboxyl group, cyano group or amino group. Preferable substituents for the phenyl group is a lower alkyl group, halogen atom or nitro group.

Examples of the guanidine compounds are methyl guanidine, ethyl guanidine, propyl guanidine, butyl guanidine, isopropyl guanidine, heptyl guanidine, octadecyl guanidine, N,N'-dimethyl guanidine, N-methyl- N'-ethyl guanidine, N-ethyl-N-butyl guanidine, N,N,N'-trimethyl guanidine, N,N,N"-trimethyl guanidine, N-methyl-N-(2-hydroxy-ethyl) guanidine, 2,2- diethoxyethyl guanidine, benzyl guanidine, (3,3- dimethyl-allyl) guanidine, N,N',N"-triallyl guanidine, N-methyl-N-allyl guanidine, cyclohexyl guanidine, methoxy guanidine, butyloxy guanidine, heptyloxy guanidine, dodecyloxy guanidine, carboxymethoxy guanidine, (3-carboxy-propyloxy) guanidine, formyl guanidine, acetyl guanidine, propionyl guanidine, butylyl guanidine, oxal guanidine, valeryl guanidine, lauroyl guanidine, cyanoacetyl guanidine, carboethoxy guanidine, carbamoyl guanidine, N-butyryl-N'-carbamoyl guanidine, phenyl guanidine, N,N'-diphenyl guanidine, N,N-dimethyl-N'-phenyl guanidine, N-phenyl-N'-otolyl guanidine, N,N-di-o-tolyl guanidine, N,N'N- triphenyl guanidine, (3-chloro-phenyl) guanidine, N- (3-nitro-phenyl)-N-N"-m-tolyl guanidine, N-o-tolyl guanidine, 4-chlorophenyl guanidine, 4-nitrophenyl guanidine, butan-l-sulfonyl guanidine, benzenesulfonyl guanidine, guanyl guanidine, o-tolyl biguanide, amino guanidine, N,N'-diamino guanidine, N-amino-N- methyl guanidine, N,N'-N-triamino guanidine, l-(2- chlorophenyl) biguanide, l, l -diethyl-5-( 3-chloro-phenyl) biguanide, l,l-diethyl biguanide, 4-amino-butyl guanidine, N-methyl-N'-guanyl guanidine, N,N-diethyl-guanyl guanidine, l-phenyl biguanide, l-(4-chlorophenyl) biguanide, l-isopropyl-5-(4-chloro-phenyl) biguanide, nitro guanidine, nitroso guanidine, Nmitro- N'-amino guanidine, N'-nitro-N-ethyl guanidine, N- nitro-N-heptyl guanidine, N-acetyl-N-cyano guanidine, N-methyl-N'-cyano guanidine, N-butyl-N'-cyano guanidine, N-lauroyl-N '-cyano guanidine, cyano guanidine, N,N-dicyano guanidine or N'-phenyl-N'-cyano guanidine, etc.

The guanidine compounds to be used also include salts of guanidine and guanidine derivatives. Examples of the salts are sulfates, nitrates, phosphates, carbonates, hydrochlorides, acetates, phthalates and benzenesulfonates of guanidine and guanidine derivatives. Of these guanidine compounds preferable are those represented by the formula (I) formula(l) wherein at least two of R to R are each of a hydrogen atom. Preferable groups represented by R, to R are each a hydrogen atom, phenyl group, amino group, guanyl group, nitro group or cyano group.

The dielectric layer in which the guanidine compound is to be contained is basically made of a high molecular weight substance having insulating properties as in the prior art. Thus employable are various high molecular weight insulating substances heretofore used for this purpose. Examples are homopolymers or copolymers of vinyl monomers as such vinyl chloride, vinyl acetate, vinyl acetal, vinylidene chloride, ethylene, styrene, acrylates and methacrylates, silicone resin, polyurethane, alkyd resin, epoxy resin, chlorinated rubber and the like. These high molecular weight insulating substances can be used alone or in admixture with one another.

According to this invention, it is critical that the dielectric layer contains at least one of the guanidine compounds in a proportion of 0.05 to weight percent. If used in a proportion of less than 0.05 weight percent, the compound fails to lower the background 4 density effectively, whereas when used in a proportion over 20 weight percent, the compound impairs the dielectric properties of the dielectric layer, hence unfavorable. More preferably, the compound is used in a proportion of 0.1 to 15 weight percent, most preferably 0.5 to 5 weight percent.

Where desired, the dielectric layer may further contain calcium carbonate, clay, titanium oxide, barium sulfate, silica, starch and like extenders which are not detrimental to the insulating properties as conventionally practiced in order to improve mat finishing, writability, printability and contrast.

As the electroconductive base sheet for the present recording material, paper, plastic sheet (synthetic paper, plastic film or the like), metal plate, etc. may be used, but paper is the most preferable in view of the low cost and amenability to processing. The base sheet preferably has an electroconductivity corresponding to a volume resistivity of 10 lO Qcm at a relative humidity of 20 percent. Therefore, in the case of the most frequently used paper base sheet, a low resistance treatment is usually applied to the paper by impregnating or coating the paper with inorganic salts, carbon black, or fine powders of aluminum, copper, nickel, etc., or polymeric electrolyte prepared, for example, from vinylbenzyl quaternary ammonium salt, sodium alginate, sodium polyacrylate, sodium polymethylene sulfonate, etc. Such electroconductive treatment is disclosed, for example, in Japanese Utility Model Publication No. 20592/ 1963 and Japanese Patent Publication No. 12,099/1963 and No. 2,878/1970,

etc.

The electrostatic recording material of this invention is produced by forming a dielectric layer over the electroconductive base sheet. The dielectric layer is formed by dissolving or dispersing at least one of guanidine compounds and the high molecular weight insulating substance in a suitable solvent such as acetone, toluene, benzene, methylethyl ketone, water, etc., with further addition of extender when so desired, to prepare a liquid composition, applying the composition to the base sheet in a suitable manner as by coating or printing and drying the applied composition.

The electrostatic recording material of this invention is used in a conventional manner. Electrical discharge is effected for example by a scanning type recording head, a gap discharge type recording head, a back electrode controlled type recording head or the like to form on the dielectric layer a negatively charged electrostatic image corresponding to the electrical signal input. The stylus may be made of a conventionally used material such as copper, copper alloy, tungsten or the like, or the combination of such metal and plastics, epoxy resin, quartz, ruby, glass or the like.

Subsequently, the electrostatic image is made visible with a positively charged developer. For this purpose, conventionally used developers are employable as they are. Generally, the developer comprises a toner and a carrier. The toner is usually a mixture of coloring agents such as carbon black, pigment, dye, etc., and resins. The carrier includes, for example, iron powder or glass beads to be used in dry system and aliphatic hydrocarbons, e.g., isoparaffine to be used in liquid system.

inasmuch as the background area is free from negative static triboelectric charges during the abovementioned steps according to this invention, the positively charged developer can be deposited effectively only on image on the recording material with a very low background density. The fixing step, in dry system, is carried out by a conventional method, for example, by heating the recording material with a hot plate, hot roll or infrared lamp or by spraying an appropriate solvent capable of dissolving the toner. In the case of liquid system, generally fixing is not necessary.

The present invention will be explained in detail, referring to Examples, but these Examples are merely illustrative, but not [imitative of the present invention. In the Examples, parts are all by weight, unless otherwise specified.

In the Examples the triboelectric charge potential on the surface of dielectric coating layer was determined by the following method, using a facsimile system having a recording head (wherein-copper wire is reinforced by epoxide resin and quartz) and two-pole magnetic brush roll which was rotated at 30 rpm. The electrostatic recording material was applied to the said system and surface triboelectric charge potential between the surface thereof and a recording head or iron powders were measured by electrometer of the rotating sector type.

EXAMPLE-l A coating composition was prepared by dissolving 100 parts of polyvinyl butyral resin (degree of butyralization: 70 mol and 2 parts of guanidine in 900 parts of methanol. The coating composition was applied an amount of 4 g/m on dry basis, onto the surface of a base sheet, which had been subjected to low resistance treatment with polyvinyl benzyl trimethylammonium chloride, to produce an electrostatic recording material.

The triboelectric charge potentialon the surface of the recording material obtained was +l5 V.

A latent electrostatic image was produced by applying signal voltage of 800 V to the recording material and wasdeveloped with a positively charged developer, whereby an extremely distinct permanent image was formed on the recording material with a low background density.

On the other hand, an electrostatic recording material was prepared as a control in the same manner as in Example 1, except that guanidine was not used. The triboelectric charge potential on the surface of the recording material obtained was 1 5 V. A latent image was produced and developed in'the sameinanner as above. The toner was attracted to the background area to result in a markedly high background density.

EXAMPLE 2 in 300 parts of methyl ethyl ketone. The base sheet was coated with the coating'eomposition 'in an amo'untof 5 material.

g/m on dry basis to produce an electrostatic recording The triboelectric charge potential on the surface of the recording material was +10 V. A distinctimage was obtained with a low background density.

On the other hand, an electrostatic recording material was prepared as a control in the same manner as above, except that methyl guanidine was not used. The triboelectric charge potential on the surface of the resulting recording material was -30 V and the background density was exceedingly high.

EXAMPLES 3 to 33- Electrostatic recording materials were prepared in the same manner as in Example 2, except that various guanidine compounds listed in Table 1 below were used in place of methyl guanidine. Each of the recording materials thus prepared had a triboelectric charge potential of positive polarity on its surface, permitting reproduction of a distinct image thereon with a low background density.

Table l Tribo- Ex. Guanidine compounds electric No. charge potential( V) N,N'-dimethyl guanidine I H 3 NCH: +10

HN=C NCH H N,N',N-trimethyl guanidine H NCH 4 H.,cN=c +10 NCH,-, H

butyl guanidine H N(CH-).CH. s HN=C +10 N-ethyI-N 'ilbuthyl guanidine NCH CH- 6 HN=C 2 J +10 a)n u H N-methyl-N-(Z-hydroxyethyl) guanidine NH, 7 nn=c +9 CH,CH;0H Hg;

2,2-diethoxy-ethyl guanidine fa 8 HN= +10 NCH H H methoxy guanidine N a 9 HN=C +10 N-=O=CH, H

butyloxy guanidine NH 10 nN-c +40 below in methyl ethyl ketone to prepare electrostatic background density. The triboelectric charge potenrecordmg materials. tials in the controls are shown in parentheses.

Table 2 Example Triobelectric No. Coating cnmpositions* charge potential (parts) (V) N,N'diphenyl guanidine 4 +5 34 polystyrene (average (|50) degree of polymeri 100 zation 37000) N,N'-diphenyl guanidine 4 +45 35 vinylacctate-vinylchloride copolymer (50:50) 100 N,N'-diphcnyl guanidine hydrochloride 4 G HN=C HCl vinylacetatc-vinylchloridc copolymer (25 75) I00 styrene-ethylacrylatc copolymer (70:30) l00 N,N'-di-o-tolyl guanidine 4 styrene-cthylacrylatc +20 copolymer (70 z 30) 60 vinylacetate-vinylchloridc copolymer (40 z 40 o-tolyl higuanidc 4 C Ha H N HN=C urethane-modified acrylic polyol (hydroxyl valuezlS) I00 Note: Methyl ethyl ketnne used was 300 parts.

The surface of the electrostatic recording material of Likewise, electrostatic recording materials were pre- Example 41 produced with addition of barium sulfate pared as controls in the same manner as above except had a glossless appearance and it was found possible to that the guanidine compounds were not used. 60 write thereon in pencil or water-soluble ink.

All the recording materials according to this inyen- EXAMPLE 42 tion had a triboelectric charge potential of positive polarity on the surfaces thereof, permitting reproduc- An electrostatic recording material was prepared by tion of distinct images thereon with a low background coating a base sheet, which had been SUbJCCtCd to low density. resistance treatment by impregnating with sodium polln contrast, all the controls in which no guanidine ystyrene sulfonate, with 5 g/m on dry basis ofa coating compound was used had a triboelectric charge potencomposition prepared by dissolving parts of stytial of negative polarity and exhibited a markedly high rene-ethyl acrylate copolymer (copolymerization ratio 12 surface of the recording material was -80 V and the background density was exceptionally high.

EXAMPLES 43 to 63 5 Electrostatic recording materials were prepared in the same manner as in Example 42, except that various guanidine derivatives as listed in Table 3 below were used in place of N,N'-diphenyl guanidine phthalate.

All the recording materials thus prepared had a tribo- 0 electric charge potential of positive polarity on the surfaces thereof, permitting production of distinct images thereon with a low background density.

Table 3 Example Guanidine compounds Triboelcctric No. charge potential lphenyl biguanide 43 HN H CNH o- N-phenyl-Ncyano guanidine 44 NH +l0 CNN=C N,N',N"-triphenyl guanidine 4-chloro-phenyl guanidine --NHC l-(4-chloro-phenyl) biguanide HN NH 47 CNH-C +7 cI-O-NH NH l-isopropyi 5-(4-chloro-phenyl) biguanide H HN NCH( .1)2 4s C-NH-( N +5 -Q-NH H 4-nitrophenyl guanidine NH 49 --NH-C +2 benzyl guanidine NH 50 -CH NHC +5 NH nitro guanidine l EXAMPLE 64 A coating composition was prepared by mixing and dissolving 500 parts of 20% aqueous emulsion of acrylic acid-styrene-methyl methacrylate terpolymer (20:40:40), 4 parts of guanidine benzenesulfonate and 100 parts of water by a propeller mixer. The resultant coating composition was applied, in an amount of 6 g/m on dry basis, onto the surface of the same base sheet as used in Example 1 to prepare an electrostatic recording material.

The surface triboelectric charge potential of the recording material was +5 V and a clear recording image was obtained with a low background density.

As a control, an electrostatic recording material was prepared in the same manner as above, except that guanidine benzenesulfonate was not used. The surface triboelectric charge potential of the recording material thus prepared was l0 V and the background density was exceedingly high.

EXAMPLES 65 and 66 Electrostatic recording materials were prepared in the same manner as in Example 64, except that in place of guanidine benzenesulfonate 3 parts of guanidine acetate and 2 parts of guanidine carbonate were used respectively.

The recording materials had surface triboelectric charge potentials of V and V respectively. permitting reproduction of clear and sharp images with a low background density.

EXAMPLE 67 A coating composition was prepared by dissolving 95 parts of vinyl chloride-methacrylic acid copolymer (85:15) and 5 parts of guanidine nitrate in 300 parts of a mixture of methyl ethyl ketone with methanol (2:1 The coating composition was applied, in an amount of 7 g/m on dry basis, onto the surface of the same base sheet as used in Example 1 to produce an electrostatic recording material.

The surface triboelectric charge potential of the resultant recording material was +10 V and a clear image was obtained with a low background density.

As a control, an electrostatic recording material was prepared in the same manner as above, except that guanidine nitrate was not used. The recording material thus obtained had a surface triboelectric charge potential of V and a very high background density.

EXAMPLE 68 A coating composition was prepared by dissolving 50 parts of polyvinyl butyral (degree of butyralization: 73 mol%), 50 parts of styrene-butylmethacrylate-laurylmethacrylate-acrylic acid copolymer (40:40:10210) and 5 parts of guanidine in 300 parts of a mixture of isopropyl alcohol and methyl ethyl ketone (1:2). The coating composition was applied, in an amount of 5 g/m on dry basis, onto the surface of the same base sheet as used in Example 1 to produce an electrostatic recording material.

During the reproduction of image on the resulting recording material on an electrostatic printer of the liquid developing type, the friction between the material and the recording head and paper feeding rolls produced a triboelectric charge potential of +3 V. Development with a liquid developer gave a clear and sharp image with a low background density.

A control prepared without using guanidine had a triboelectric charge potential of 5 V on its surface and resulted in an. exceedingly high background density.

' What we claim is:

1. ln an electrostatic recording material consisting essentially of an electroconductive base sheet having a dielectric layer on which a negatively charged electrostatic image of electrical signal is to be formed, an improvement which is characterized in that said dielectric layer contains at least one of guanidine compounds selected from the group consisting of guanidine, guanidine derivatives, and salts thereof in a proportion of 0.05 to 20 weight percent.

2. The electrostatic recording material according to claim 1 in which said guanidine compound is at least one of a) guanidine and b) guanidine derivatives represented by the formula wherein each of R,, R R R and R is a hydrogen atom, aliphatic hydrocarbon group, substituted aliphatic hydrocarbon group, alkoxyl group, substituted alkoxyl group, acyl group, substituted acyl group, phenyl group, substituted phenyl group, amine group, substituted amino group, guanyl group, substituted guanyl group, nitro group, nitroso group, cyano group or RSO R" being a phenyl or alkyl group and c) salts of said guanidine and guanidine derivatives.

3. The electrostatic recording material according to claim 2 in which said aliphatic hydrocarbon group is an alkyl group, alkenyl group or alicyclic group.

4. The electrostatic recording material according to claim 2 in which said substituted aliphatic hydrocarbon group, substituted alkoxyl group, substituted acyl group, substituted amino group or substituted guanyl group has a substituent of a hydroxyl group, alkoxyl group, amino group, phenyl group, carboxyl group, cyano group, nitro group, nitroso group or halogen atom.

5. The electrostatic recording material according to claim 2 in which said substituted phenyl group has a substituent of an alkyl group, halogen atom, nitro group, hydroxyl group, alkoxyl group, amino group, carboxyl group, cyano group or nitroso group.

6. The electrostatic recording material according to claim 2 in which each of said R, to R is a hydrogen atom, phenyl group, amino group, guanyl group, nitro group or cyano group.

7. The electrostatic recording material according to claim 2 in which at least two of R, to R are each a hydrogen atom.

8. The electrostatic recording material according to claim 2 in which at least two of R, to R, are each a hydrogen atom, the .rest of R, to R if any, being a hydrogen atom, phenyl group, amino group, guanyl group, nitro group or cyano group.

9. The electrostatic recording material according to claim 1 in which said guanidine compound is contained in a proportion of 0.1 to 15 weight percent.

10. The electrostatic recording material according to claim 9 in which said guanidine compound is contained in a proportion of 0.5 to 5 weight percent.

Q Patent No. 3,930.080 Dated December 30. 1975 lnventor(s) Tadashi Tanimoto et a1.

It is certified that error appears in the above-identified patent Q and that said Letters Patent are hereby corrected as shown below:

Column 1, line 33 change "presence" to -process-. Column 3 line 46 change "the formula (I) formula (1)" to -the foregoing formula (I)--, Column 12, line 45 after the formula, insert --+5-. Column 16, line 29 change "amine" to --amino--.

Signed and Scaled this {SEAL} fourth Day of May 1976 Q A ttest:

RUTH C. MASON I C. MARSHALL DANN Aneslmg Officer Commissioner uj'lani '11s and Trademarks 

1. IN AN ELECTROSTATIC RECORDING MATERIAL CONSISTING ESSENTIALLY OF AN ELECTROCONDUCTIVE BASE SHEET HAVING A DIELECTRIC LAYER ON WHICH A NEGATUIVELY CHARGED ELECTROSTATIC IMAGE OF ELECTRICAL SIGNAL IS TO BE FORMED, AN IMPROVEMENT WHICH IS CHARACTERIZED IN THAT SAID DIELECTRIC LAYER CONTAINS AT LEAST ONE OF GUANIDINE COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF GUANIDINE, GUANIDINE DERIVATIVES, AND SALTS THEREOF IN A PROPORTION OF 0.05 TO 20 WEIGHT PERCENT.
 2. The electrostatic recording material according to claim 1 in which said guanidine compound is at least one of a) guanidine and b) guanidine derivatives represented by the formula
 3. The electrostatic recording material according to claim 2 in which said aliphatic hydrocarbon group is an alkyl group, alkenyl group or alicyclic group.
 4. The electrostatic recording material according to claim 2 in which said substituted aliphatic hydrocarbon group, substituted alkoxyl group, substituted acyl group, substituted amino group or substituted guanyl group has a substituent of a hydroxyl group, alkoxyl group, amino group, phenyl group, carboxyl group, cyano group, nitro group, nitroso group or halogen atom.
 5. The electrostatic recording material according to claim 2 in which said substituted phenyl group has a substituent of an alkyl group, halogen atom, nitro group, hydroxyl group, alkoxyl group, amino group, carboxyl group, cyano group or nitroso group.
 6. The electrostatic recording material according to claim 2 in which each of said R1 to R5 is a hydrogen atom, phenyl group, amino group, guanyl group, nitro group or cyano group.
 7. The electrostatic recording material according to claim 2 in which at least two of R1 to R5 are each a hydrogen atom.
 8. The electrostatic recording material according to claim 2 in which at least two of R1 to R5 are each a hydrogen atom, the rest of R1 to R5, if any, being a hydrogen atom, phenyl group, amino group, guanyl group, nitro group or cyano group.
 9. The electrostatic recording material according to claim 1 in which said guanidine compound is contained in a proportion of 0.1 to 15 weight percent.
 10. The electrostatic recording material according to claim 9 in which said guanidine compound is contained in a proportion of 0.5 to 5 weight percent. 